1. Field of the Invention
The present invention relates to a headrest. More particularly, the present invention relates to a movable headrest which is used for a seat for a conveyance and is improved so as to suppress occurrence of whiplash.
2. Description of Related Art
Conventionally, it is widely known to employ a headrest for a seat for a conveyance. It is also known to provide a movable headrest by combining a portion that is fixed to a seat back and a portion that can be moved upward and downward relative to the seat back (Japanese Patent Application No. 2013-169945). With a headrest having the structure described in JP 2013-169945A, it is possible to suppress occurrence of whiplash even if the head of an occupant moves in the upper-lower direction relative to the headrest when the rear side of a conveyance is hit (in other words, when a rear collision occurs), because a part of the headrest moves in accordance with the behavior of the head of the occupant.
However, there is still room for improvement in the technology described in JP 2013-169945A. In the technology described in JP 2013-169945A, unless the entire movable member is shifted rearward, the locking is not released and the upward/downward movement is not allowed. Further, in the configuration described in JP 2013-169945A, a member that prevents movement of the movable member relative to a base member is disposed in a space in a portion that is substantially recessed in a sectional view and that is provided in the base member or the movable member. Therefore, the locking is not released unless this member is pushed away, and as a result of pushing this member away to release the locking, a relatively large clearance is formed in the front-rear direction. Thus, backlash of the movable member may occur.